Mandarin fruit bug

[lorca lad]

Hi,

Hope someone can help me with this problem ....... I sprayed the mandarin bushes earlier in the year and again, just as the fruit was forming ..... used  an insecticide and fertiliser, as recommended by the local  co-op.

The fruit forms perfectly, but then drops off the tree. Each mandarin has a small brown spot on it and this goes softer after 2 days, then when it is cut open, it has a maggot inside.

I have taken some fruit off the tree before it is fully ripe, but this is also affected in the same way, several days later.

Last year, I had the same problem with the oranges, but at the moment, they seem ok.

Any help much appreciated.

Regards
L.L.